Photographic silver halide emulsion containing carbamate accelerator



United States Patent O tion of Japan No Drawing. Filed Nov. 27, 1962, Ser. No. 240,454 laims priority, application .lapan, Dec. 26, 1961,

1 Claim. (Cl. 96-467) This invention relates to a photographic emulsion of silver halide and more particularly to a photographic emulsion containing accelerator.

it is desirable to accelerate the development of photographic emulsion of silver halide, that is, to shorten the time necessary for attaining the definite photographic characteristics such as a definite density, a definite sensitivity, a definite gamma, and the like, or to make it possible in a definite time of development to attain the photographic characteristics which cannot be attained in a short time of development unless a new method is employed. In order to attain these objects, it has been proposed to add an accelerator such as quaternary ammonium salts. However, in most cases, such compounds, especially quaternary salts have various detrimental secondary effects on the emulsion such as the deterioration of the preservation property of emulsion and of the adhesion between the base and the emulsion and the like.

It is the object of this invention to prepare a photographic emulsion of silver halide containing a new accelerator having no such deterimental secondary effects.

This object can be attained by adding to the photographic emulsion at least one compound selected from the group consisting of N-[(dialkylamino)alkyl]carbamates represented by the following formula:

ANHC0.0RB

R2 where R R and R represent alkyl group, R and R may combine to form a ring, A represents alkylene group and the total number of carbon atoms contained in R I R R and A is not less than9, and their salts.

Examples of compounds employed in this invention are as follows:

(III) '3,lh 3,536 Patented Dec. 29,1964

The compounds mentioned above are generally produced by dehydrochlorination of N,N-dialkylor N,l I- polymethyleneaminoalkyl amine and chlorocarbomc ester.

The amount of the compounds added to the photographic emulsion varies according to the sorts of emulsion and agent. in general, it 'is preferable to add in a proportion of 0.1 to 10 g. of agent to 1 mole of silver halide contained in the photographic emulsion.

Photographic emulsions are prepared in the following three stages: (1) The emulsification and digestion (first ripening) of the silver halide, (2) removal of excess of salts by Washing with water and the like, (3) second digestion (after ripening) to increase the sensitivity. The compound of this invention may be added to the emulsion in any stage mentioned above, but it is most preferable to addafter the second digestion and before coating. These compounds are dissolved in a solvent which has no detrimental effect on the emulsion, for example, water,

lower alcohols such as methanol, ethanol and the like, ketones' such as acetone.

Emulsions of silver chloride, silver bromide, silver chlorobromide, silver iodobromide, silver chloroiodobromide can be employed in this invention. The emulsion of silver chlorobrornide gives a good result when used for material for the graphic arts.

The emulsion may be chemically sensitized by an unstable compound containing sulfur such as ammonium thiosulfate, allyl thioureaand others (for example, ref. P. Glafkides Chimie Photographique, 2eme Edition Photocinema 1957, pp. 297-299, Paul Montel, Paris) and/or compounds of gold such as a complex of monovalent gold and thiocyanic acidtref. ibid., p. 301), accord to the well-known method. The emulsion may be optically sensitized by sensitizing dyes such as cyanine dyes and merocyanine dyes (for example, ref. Shinichi Kikuchiet al., Handbook of. Scientific Photography, 1959, pp. 15-24, Maruzen, Japan). The emulsion may be stabilized by heterocyclic compounds such as hometriazole, 1-phenyl-S-mercaptotetrazole and the like. The emulsion may also contain the hardening agent such as chromium alum or formaldehyde (ref. ibid., pp. 29-47). In order to facilitate the coating, the emulsion may contain a surface-active agent.

The developing solution suitable for developing the emulsion of this invention is the one which has a high pH value such as higher than 10 and contains hydroquinone as developer. 7

It is well known that a certain type of alkylamine has the accelerating action (U.S.P. No. 2,515,147, No. 2,541,889, No. 2,605,183). The feature of the compound of this invention is that two nitrogen atoms is contained and one of them is attached to (3:0 group. Alkylarnine which contains only one nitrogen atom has not such accelerating action as the compound of this invention. Polyamine compounds are well known as the reduction sensitizer. The sensitizing action of such reduction sensitizer appears by ripening and is different from that of the compounds of this invention. The former type of polyamine deteriorates the preservation property of emulsion and forms fogs in the lapse of time, while the compounds of this invention does hardly deteriorate the preservation property of emulsion.

In order to facilitate the understanding of this invention, an example will be given hereafter. It should be understood that the invention is not limited by the example but limited by the appended claim.

Example Five samples were prepared by adding the following amounts of N-[(dialkylamino)alkyl]carbamates in the form of methanol solution to the emulsion of silver chlorobromide which contains 30 mole percent of silver Results of development for 1'30", 2'15" or 3' are bromide and is optically sensitized by merocyanine dyes, summarized in the following table.

Relative Gamma Fog Amount sensitivity Compound (g./1 mole) (reference) (I) 5.7 37 70 103 6.3 10.8 9.5 0.04 0.04 0.05 5.0 50 75 110 0.9 11.0 0.3 0.04 0.04 0.05 2.3 48 72 100 7.0 10.3 9.5 0.04 0.04 0.05 0.81 so 92 103 9.5 10.5 8.9 0.04 0.05 0.05

giving the resulting emulsion on a film base and then drying.

results in the remarkable increases in sensitvity Amount of As seen from the table, the addition of compounds and gamma when the development was carried out for 1 /2 minutes but has little effect when the development was Sample additive (gJl carried out for 3. That is, the addition of compounds g f g 20 results in the increase in the initial rate of development.

What is claimed is: (i) 0 (reference) A photographic emulsion of silver halide characterized 11} Compound (I) .g m that the said emulsion contains at least one compound 5: selected from the group consisting of N-[(dialkylamino) (v) Compound (IV) .8 g- 25 alkyl]carbamates represented by the following general formula: Then, sensitornetry was carried out. In sensitometry a tungsten lamp (2666 K.) was used as a light source. A film was exposed for to the light passing through an optical wedge having 0.1 of the step difference and then developed at C. in a developer of the following wherein each of R R and R represents an alkyl group containing not more than 4 carbon atoms, A represents formula:

alkylene group containing not more than 5 carbon atoms, Warm water cc 500 and the total number of carbon atoms contained in R Sodium sulfite anhydrate g R R and A is not less than 9, and the mineral acid Para-formaldehyde g 7.5 salts of said carbamates.

ggigg z g j if g References Cited by the Examiner Hydroquinone g 22.5 UNITED STATES PATENTS bromlde 2,937,090 5/60 Kennard et al. 96-107 Addltlonal Water Balm 2,944,902 7/60 Carrol et a1. 96 107 Total liters 1 NORMAN G. TORCHIN, Primary Examiner. 

